Nucleosides, and in particular, 1,3-oxathiolanes and their analogues and derivatives are an important class of therapeutic agents. For example, a number of nucleosides have shown antiviral activity against retroviruses such as human immunodeficiency viruses (HIV), hepatitis B virus (HBV) and human T-lymphotropic virus (HTLV).
The most potent anti-HIV compounds thus far reported are 2',3'-dideoxynucleosides, more particularly, 2',3'-dideoxycytidine (ddC) and 3'-azido-2',3'-dideoxythymidine (AZT). These compounds are also active against other kinds of retroviruses such as the Moloney murine leukemia virus. However, clinically, both compounds are toxic.
A structurally distinct class of compounds known as 2-substituted-5-substituted-1,3-oxathiolanes has been found to have superior antiviral and antiretroviral activity without cell toxicity. See, e.g., EP 0382526A and WO 91/17159 the disclosures of which are incorporated herein by reference.
Because of the increasing incidence and the life-threatening characteristics of AIDS, there is a great need to develop a general synthetic scheme for substituted 1,3-oxathiolanes which is efficient, amenable to large scale, inexpensive and based on readily available starting material. It is therefore an advantage of the present invention to provide synthesis of substituted 1,3-oxathiolanes that is readily feasible.